Forming roller for corrugated fin

ABSTRACT

Forming rollers having a tooth tip concave portion at the tip of a tooth tip portion, a tooth bottom convex portion at a bottom of a tooth bottom portion and louver cutter at an oblique line portion between the tooth tip portion and the tooth bottom portion. A radius of an arc-shaped portion of the tooth tip concave portion at front side of rotational direction is set to be larger than a radius of an arc-shaped portion of the tooth tip concave portion at a rear side of the rotational direction. A radius of an apex portion of the tooth tip portion at the front side is set to be smaller than a radius of an apex portion of the tooth tip portion at the rear side and louver cutter at the oblique line portion is formed to have a predetermined interval from the apex portions of tooth tip portion. Therefore, flat folded portions having substantially the same curvature at both shoulder portions thereof horizontal are formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Application 5-223696, filedin Japan on Sep. 8, 1993, from which priority is claimed. The content ofthis document is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of forming rollers forproducing corrugated fins utilized in heat exchangers for airconditioners or radiators, etc.

2. Description of the Related Art

Conventionally, the corrugated fins utilized for heat exchangers have afolded portion with an arc-shape. The corrugated fin having thearc-shaped folded portion was decreased contact area with a flat tubedisposed so as to contact both side of the folded portion whenassembled. Consequently, heat transmission efficiency between thecorrugated fin and the flat tube is decreased and the resistance to airflowing between the corrugated fin is increased.

To solve the above problems, a corrugated fin having a folded portion,which is shaped flat, is suggested in Japanese Patent UnexaminedPublication (KOKAI) 55-110892. The corrugated fin having a flat foldedportion is formed by a pair of forming rollers, with one being shown inan enlarged view in FIG. 4. Forming roller 20 has concave portion 21 atthe tip of the tooth and convex portion 22 at the bottom of the tooth.The corrugated fin is machined by making fin material pass through anengaged and rotated pair of forming rollers 20. Concave portion 21,shapes an arc having a predetermined radius r. Louver cutters 23 areentirely formed on the oblique lines between concave portions 21 andconvex portions 22.

When a corrugated fin is formed by a pair of forming rollers 20, 20, theformed corrugated fin has flat folded portion 26 slants as shown in FIG.7. Each curvature, at both ends of the folded fin, is different on theleft and right sides, so that enough contact area between the corrugatedfin 25 and a tube can not be secured.

As shown in FIG. 5, the pair of forming rollers 20, 20 engage togetherand rotate together in the direction of the arrow. Fin material W ismachined (or formed, processed) by passing through the pair of rollers20, 20. Fin material W pinched between concave portion 21 of tooth tipand convex portion 22 of tooth bottom is push up at "a" in FIG. 5 byconvex portion on 22, so that a strong tension is caused at fin materialW. Therefore, the portion "a" of fin material W receives a strongburnish operation (operation to strongly rub surface). At this time at"b" portion, louvers have been completely cut on fin by louver cutter23. At "c" portion, fin material W is still on louver cutter 23 andlouvers have not been completely cut yet.

Next as shown in FIG. 6 at "d", louvers are completely cut and finmaterial W is drawn, so that the tension is released and burnishoperation by convex portion 22 is decreased. Like this, fin material Wreceives burnish operation strongly only at right side (front side ofrotational direction) thereof between concave portion 21 and convexportion 22. When the tension operates to fin material W, flat foldedportion is formed. Portion "b" is bent at the side of forming roller andportion "c" is bent on louver cutter 23.

Consequently, both shoulder portions at flat folded portion of formedfin material do not have the same curvatures. A rotational side (formingdirectional side) shoulder has larger curvature than the other sideshoulder. Accordingly, as shown in FIG. 7, formed corrugated fin has aslanted, flat folded portion 26.

SUMMARY OF THE INVENTION

An object of the present invention is to provide forming rollers forcorrugated fin enabling formation of an excellently shaped corrugatedfin having a horizontal flat folded portion with substantially the samecurvature at both shoulder portions.

To achieve the above object, the forming rollers of the presentinvention comprise tooth tip portions having tooth tip concave portionsat the tip thereof. The tooth tip concave portions are formed from firstand second arc-shaped portions having a first radius at the front sideof the rotational direction by the forming roller and a second radius atthe rear side of the rotational direction of the forming roller, thefirst radius being larger than the second radius. Further, the tooth tipconcave portion has first apex portion at the front side of rotationaldirection and second apex portion at the rear side of rotationaldirection. A radius of the first apex portion is smaller than a radiusof the second apex portion. Tooth bottom portions have tooth bottomconvex portions at the bottom thereof and are disposed alternately withtooth tip portions. Louver cutters, for cutting louvers are disposed atan oblique line portions between the tooth tip portions and the toothbottom portions the louver cutters at the oblique line portions beingformed to have a predetermined interval from each the apex portions.

The corrugated fin is formed by utilizing a pair of forming rollershaving such a constitution. The pair of forming rollers are disposed toengage and rotate each other. Fin material of thin metal plate is fedinto the pair of rollers. The tooth tip portion of a first formingroller engages the tooth bottom portion of a second forming rolleralternately. Fin material is pinched between the first and secondrollers. Louvers are cut by louver cutter on the oblique line portion.The corrugated fin is thus produced by engagement of the tooth tip andbottom portions. The concave portion of the tooth tip portion and theconvex portion of the tooth bottom portion engage to pinch fin materialtherebetween. By rotation of the rollers, a flat folded portion isformed. Since a radius of an arc-shaped of a concave portion towards thefront of the rotational direction is bigger than a radius of anarc-shaped of a concave portion at the rear side of the rotationaldirection, convex portion of the tooth bottom portion push up finmaterial with delay. Therefore a position to push up fin material slidesto rear side of rotational direction. Fin material between the concaveportion and convex portion receives burnish operation at its centerarea, not at front side of rotational direction.

At an apex portion of the tooth tip portion at front side of rotationaldirection, tension operates on fin material. The louvers are notcompletely cut. A flat folded portion of the fin material is formed by aportion, which extends between the apex portion at front side ofrotational direction and the end of louver cutter. A radius of the apexportion at front side of rotational direction is smaller than a radiusof the apex portion at rear side of rotational direction. Since thelouver cutter on the oblique line portion is formed with a predeterminedinterval from the apex of the tooth tip portion, the fin material is notfolded by only the louver cutter at the front side of rotationaldirection conventionally, and the fin material is folded with eachcurvature of each shoulder portion of the flat folded portion beingsubstantially the same.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, and advantages will be clear as well as thefunctions of related parts, after review of the following detaileddescriptions, the appended claims and drawings, all of which form a partof the specification. In the drawings:

FIG. 1 is a partially enlarged front view of a forming roller of anembodiment of the present invention;

FIG. 2 is a partially enlarged cross sectional view of engaged formingrollers of an embodiment;

FIG. 3 is a front view of a corrugated fin formed by using the formingrollers of the present invention;

FIG. 4 is a partially enlarged front view of a related forming roller;

FIG. 5 is a partially enlarged cross sectional view of related engagedforming rollers;

FIG. 6 is a partially enlarged cross sectional view of related engagedforming rollers;

FIG. 7 is a front view of a corrugated fin formed by the related formingrollers; and

FIG. 8 is a schematic view of forming corrugated fin by a pair offorming rollers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to paired forming rollers for producing acorrugated fin. The corrugated fin is utilized for a core portion ofheat exchanger, such as a radiator having a core portion consisting of aplurality of flat tubes and a plurality of corrugated fins disposedalternately between an upper and a lower tanks. A pair of formingrollers 1, 1 are shown in FIG. 8. Fin material W made of a thin metalplate is fed between the rollers. Fin material W is corrugated as itpasses through the rollers. FIG. 1 shows a partial enlargement frontview of forming roller 1 for corrugated fin. Forming roller 1 has toothtip portion 2 and tooth bottom portion 3 formed alternately andcontinuously at the outer periphery of roller 1 and has louver cutter 4for forming louver cut with helical shape at an oblique line portionbetween tooth tip portion 2 and tooth bottom portion 3.

Tooth tip portion 2 has tooth tip concave portion 2a. Tooth bottomportion 3 has tooth bottom convex portion 3a. A radius R1 of arc-shapedportion of tooth tip concave portion 2a at front side of rotationaldirection is formed to be larger than a radius R2 of arc-shaped portionof tooth tip concave portion 2a at rear side of rotational direction.Tooth tip portion 2 has apex portion 2b at front side of rotationaldirection and apex portion 2c at rear side of rotational direction. Aradius R3 of apex portion 2b is smaller than a radius R4 of apex portion2c. A louver cutter 4 formed at an oblique line portion is formed with apredetermined interval H from apex 2b and apex 2c of tooth tip portion2. In other words apexes 2b and 2c protrude from the tip of louvercutter 4 by the interval H.

When a corrugated fin is formed by forming roller having the aboveconstitution, fin material W formed of a thin metal plate is passedbetween the pair of forming rollers 1, which are disposed to engage eachother and rotate. Tooth tip portion 2 of one forming roller 1 engagestooth bottom portion 3 of the other forming roller 1. Fin material W ispinched between the engaged rollers. Louvers are cut on fin material Wby louver cutter 4 of the oblique line portion and corrugated fin isformed by an engagement of tooth tip portion 2 and tooth bottom portion3.

An engaging state by the pair of rollers is described as follows. Asshown in FIG. 2, tooth tip concave portion 2a of tooth tip portion 2engages with tooth bottom convex portion 3a of tooth bottom portion 3 inorder to pinch fin material W therebetween. A flat folded portion of finmaterial W is formed. Since radius R1 of arc-shaped portion of tooth tipconcave portion 2a at the front side of rotational direction is set tobe larger than radius R2 of arc-shaped portion of tooth tip concaveportion 2a at the rear side of rotational direction as shown in FIG. 1,a position where tooth bottom convex portion 3a pushes up fin material Wis delayed and slid to rear side of rotational direction. Therefore, finmaterial W between tooth tip concave portion 2a and tooth bottom convexportion 3a receives a burnish operation around its center, not the frontside of the rotational direction.

Since a tension is applied to fin material W, at apex 2b of tooth tipportion 2 at front side of rotational direction, louvers are not cutcompletely. Flat folded portion of fin material W is formed by anextended portion, which extends between apex portion 2b and the end oflouver cutter 4. A radius of apex portion 2b at front side of rotationaldirection is smaller than a radius of apex portion 2c at rear side ofrotational direction and louver cutter 4 of the oblique line portion isformed to have a predetermined interval from apexes 2b and 2c.Therefore, fin material W is not folded on louver cutter 4 at front sideof rotational direction as conventional and is folded to havesubstantially the same curvature at both shoulder portions of the flatfolded portion.

In case of forming with substantially the same curvature of bothshoulder portions of the flat folded portion, each radius of both apexportions of tooth tip portion 2 is required to be the same in theory. Informing, the flat folded portion is formed under a state that tension isapplied to fin material W at rear side of rotational direction. A thismoment, the cutting of louvers is finished. Therefore, fin material W isfolded by only apex portion 2c at rear side of rotational direction.

In the contrary, the cutting of louvers is not finished completely undera state where tension is applied to fin material W at apex portion 2b.The flat folded portion of fin material W is formed by the extendedportion extended between apex portion 2b and the end of louver cutter 4.Therefore, fin material W is folded in order to have substantially thesame curvature at both shoulder portions of the flat folded portion.Formed corrugated fin 5 has horizontal flat folded portion 6 which isnot slanted as shown in FIG. 3, so that corrugated fin having excellentshape is formed.

When a corrugated fin for heat exchanger for an automotive airconditioner, for example, is produced by paired forming rollers in thepresent invention, paired forming rollers are accumulated with apredetermined intervals corresponding to intervals of louvers, in otherwords paired forming rollers are disposed side-by-side across a width ofa fin material. Therefore, a number of forming rollers are decided basedon a width of the core of the heat exchanger, in other words a number offormed louvers corresponds to a number of parts of forming rollers.

Second apex portion 2c is disposed farther from a center of formingroller 1 than first apex portion 2b. Second apex portion 2c is disposedouter periphery side from first apex portion 2b. Therefore, a radius ofa first circle made by connecting adjacent first apex portions 2b offorming roller 1 is smaller than a radius of a second circle made byconnecting adjacent second apex portions 2c of forming roller 1.

The present invention has been described in connection with what ispresently considered to be the most practical and preferred embodimentthereof. However, the invention is not meant to be limited to thedisclosed embodiment, but rather is intended to cover all modificationsand alternative arrangements included within the spirit and scope of theappended claims.

What is claimed is:
 1. A pair of forming rollers for forming acorrugated fin, each forming roller comprising:tooth tip portions havingtooth tip concave portions at a tip thereof, said tooth tip concaveportions being formed from first and second arc-shaped portions having afirst radius at a front side of a rotational direction of said rollers,and second radius at a rear side of said rotational direction, saidfirst radius being larger than said second radius, said tooth tipconcave portions having a first apex portion at said front side and asecond apex portion at said rear side, a radius of said first apexportion being smaller than a radius of said second apex portion; toothbottom portions having tooth bottom convex portions at a bottom thereofand being disposed alternately with tooth tip portions; louver cuttersfor cutting louvers disposed at oblique line portions between said toothtip portions and said tooth bottom portions, said louver cutters at theoblique line portions being formed to have a predetermined interval fromeach said apex portions.
 2. A machine for forming a corrugated fin usingpaired rollers according to claim 1, comprising:a plurality pairedrollers disposed side-by-side across a width of a fin material.
 3. Amachine for forming a corrugated fin according to claim 2, wherein anumber of formed louvers corresponds to a number of parts of saidrollers.
 4. A pair of forming rollers for forming corrugated fin, eachforming roller comprising:tooth tip portions having tooth tip concaveportions at a tip thereof, said tooth tip concave portions being formedfrom first and second arc-shaped portions having a first radius at afront side of rotational direction of said rollers, and a second radiusat rear side of said rotational direction, respectively, said firstradius being larger than said second radius, said tooth tip concaveportions having a first apex portion at said front side and a secondapex portion at said rear, a radius of a first circle made by connectingadjacent first apex portions of said forming roller being smaller than aradius of a second circle made by connecting adjacent second apexportions of said forming roller; tooth bottom portions having toothbottom convex portions at a bottom thereof and being disposedalternately with tooth tip portions; louver cutters for cutting louversdisposed at oblique line portions between said tooth tip portions andsaid tooth bottom portions, said louver cutters at the oblique lineportions being formed to have a predetermined interval from each saidapex portions.
 5. A pair of forming rollers for forming a corrugated finfor an automotive air conditioner, said pair of forming rollers includesfirst forming roller and a second forming roller, each forming rollercomprising:tooth tip portions having tooth tip concave portions at thetip thereof, said tooth tip concave portions being formed from first andsecond arc-shaped portions, which are continuously connected, said firstand second arc-shaped portions having a first radius at a front side ofrotational direction of said rollers and a second radius at a rear sideof said rotational direction, respectively, said first radius beinglarger than said second radius, said tooth tip concave portions having afirst apex portion at said front side and a second apex portion at saidrear side to position both ends of said first and second arc-shapedportion, a radius of said first apex portion being smaller than a radiusof said second apex portion; tooth bottom portions having tooth bottomconvex portions at the bottom thereof and being disposed alternatelywith tooth tip portions; louver cutters for cutting louvers disposed atoblique line portions between said tooth tip portions and said toothbottom portions, said louver cutters at the oblique line portions beingformed to have a predetermined interval from each said apex portions. 6.A pair of forming rollers for forming a corrugated fin, each rollercomprising:a plurality of teeth, each tooth including a tooth tipportion and a tooth bottom portion; lower cutters formed between saidtip portion and said bottom portion; wherein said tooth tip portionincludes first, second, third, and fourth arc-shaped portions, eachhaving a different radii; and wherein said tooth bottom portion includestwo concavities which interact with said arc-shaped portions to formsaid corrugated fin.